JPS6228001B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to tires, and more particularly to tire treads and pneumatic tires and their manufacture. The tire tread can be molded and cured integrally with the tire carcass to form a complete tire, or the tread can be formed separately from the carcass and then bonded thereto to form a complete tire. The separately formed tread may take the form of a tread strip of length at least equal to the circumference of the tire in which it is incorporated, the ends of the tread strip being attached to the carcass during tire manufacture. Combined when placed on top. Separately formed treads can be applied to a new carcass or to the carcass of a used tire from which the original tread has been removed. Intricate and precise design of ribs and blocks that provide a surface groove network for the purpose of allowing conventional tires to be driven on wet pavement surfaces without excessive water build-up between the conventional tire tread and the pavement surface. It has a pattern. Such water build-up significantly impairs the adhesion between the tire and the pavement surface, thus leading to reduced braking and handling performance. These conventional tire treads require complex and expensive molds to form the tread pattern. The present invention provides a new type of tire tread and a pneumatic tire incorporating the new tread (as well as a method of manufacturing the tread and tire), which tire tread provides an alternative tire tread that maintains good adhesion on wet pavement surfaces. This method is economically advantageous as it eliminates the need for complex patterned molds. In accordance with a first aspect of the invention, a tire tread of elastomeric material is formed to provide randomly distributed and randomly oriented interconnected passageways extending from the tread surface substantially throughout the tread. is provided. The porosity of the tread (as defined later) is 10
% to 60%, preferably 25% to 40%. The interconnected passageways constitute pores within the tread, and the total volume of the pores, expressed as a fraction of the total volume of the tread, is referred to herein as the "void content" of the tread. Expressed as a fraction of volume.The volume of elastomeric material bounding between interconnected passageways is defined as the "solid content" of the tread.
Contcnt). From the above definition, it will be seen that "porosity" + "solids content" is equal to the total volume of the tread. Therefore, when the porosity is X%, the solids content should be (100-X)%. In the tire tread, the average cross-sectional area of the passages may be greater or less than the cross-sectional area of the adjacent tread material bounding the passages. In the latter case (i.e. relatively small passages), the tire may be called a porous tire. In the tire tread, the porosity may be substantially homogeneously distributed throughout the tread.
Alternatively, the porosity can vary in different regions in the tread substantially according to a predetermined pore distribution pattern. Examples of pore distribution patterns that fall within the scope of this invention include patterns in which porosity decreases or increases as the distance radially inward from the tread surface in contact with the road increases when the tread is made part of a tire. It may be something that people are accustomed to doing. Alternatively or additionally, the pattern may be such that the porosity decreases or increases with increasing distance inwardly and laterally from the lateral edges of the tread. Other pore distribution patterns are possible within the scope of the invention. The tire tread contains numerous discrete regularly or preferably irregularly shaped particles of elastomeric material, preferably of the type used as tread stocks in conventional tires; It may also be scrap tires or material obtained from scrap tire stock.
The particles may have a substantially uniform size, or they may have at least two different sizes. The particles range from 6.5 x 10 ^-5 cc to 15 c.c., preferably from 5 x 10 ^-4 cc to 4
It can have a volume in the range of ×10 ⁻² cc. The particles may have a hardness or hardness range from 30 to 85 Shore A. The selected particles of different size and/or hardness can be distributed in the tread substantially according to a predetermined particle distribution pattern. Preferably, the particles may be bonded to each other into agglomerates. The particles may be joined by interparticle melting, which may consist of bridging the material of adjacent particles at their points of mutual contact. Alternatively, the particles may be bound together into agglomerates by a binder matrix. The binder matrix may be a thermosetting material or may consist of a binder material that solidifies and binds the particles together by forming a binder matrix with the particles. The binder material can be a thermoset resin or a reaction mixture that forms a polymer when cured, and the polymer can be polyurethane, polyurea, polyamide, polybutadiene or polypropylene. Preferably, when the tread is part of a tire, the surface of the tread that contacts the pavement surface does not have any regular pattern such as blocks, ribs, slots or grooves. According to a second aspect of the invention there is provided a pneumatic tire comprising a carcass and a tire tread according to the first aspect of the invention. The tire may be a radial tire incorporating a tread reinforcement breaker provided between the carcass and the tread;
Alternatively, the tire may be a cross-ply tire or the tire may be a belted bias tire incorporating a tread reinforcement breaker between the carcass and the tread. According to a third aspect of the invention there is provided a method of manufacturing a tire tread according to the first aspect of the invention, comprising the step of bonding powdered elastomeric material to form the required shape of the tread. The particles may be bonded by an interparticle melting process, and if the particles consist of uncured rubber, the melting may consist of crosslinking the material of adjacent particles at their points of mutual contact. Alternatively, the particles may be bonded together by forming a mixture of the particles and a binder material. The formed mixture can be at least partially cured to form an agglomerate. The forming step may be carried out by extruding the mixture through a die whose orifice is formed into the desired cross-sectional shape of the tread, and the extruded tread may be cured immediately after it leaves the die. The extruded tread may be cut into discrete lengths substantially equal to the circumference of the tire in which the tread is to be incorporated. Alternatively, the forming method may include placing the mixture in a mold having the desired tread strip shape and dimensions, then partially curing the mixture within the mold, and finally removing the tread strip from the mold. It may be performed by a process. The mold may be annular so as to produce a tread band in the shape of a seamless tread loop. The method of manufacturing tire treads involves pulverizing the particles, which may be granulation of rubber sheets or blocks, which may be cryogenically frozen to promote granulation, or by cutting a scrap tire tread. It includes a step of forming. When the material is granulated, it can be sieved to select particles having a relatively uniform size from the relatively non-uniformly sized particles produced by the granulation process. According to a fourth aspect of the invention, the method of the invention comprises forming a tire tread by the method of the third aspect of the invention, applying the tire tread to a tire carcass, and joining the tread and carcass assembly. A method of manufacturing a tire according to two aspects is provided. The tread is extruded onto the carcass, the assembly is placed in a mold, and once the tire is substantially fully cured, the tire can be removed from the mold. Alternatively, the carcass is placed in a mold, a mixture of elastomer particles and binder material is injected around the carcass in the mold, the assembly is cured in the mold by applying heat and pressure, and the tire is substantially completely cured. Once cured, the tire can be removed from the mold. As a further variant, the treads may be preformed as tread strips or tread bands and the preformed treads may be connected to the carcass. Bonding of the tread to the carcass is accomplished by the use of adhesive. The tire carcass and associated tire tread can be placed in an unpatterned mold and cured by applying heat and pressure. In manufacturing a tire according to this fourth aspect of the invention, the tire carcass may first be at least partially precured, and additionally or alternatively, the tire tread may be substantially uncured. The tire carcass may be a used tire carcass from which the original tire has been removed. The principle by which the size of mineral particles can be selected to give a given porosity is relevant to the "Delugrip"® road surface material, which contains selected sized mineral particles embedded in an asphalt binder. It is written as follows. It is believed that the same principles are applicable to the manufacture of tire treads according to the present invention. These principles were published in February 1970 in the Proceedings of the Association of Asphalt Pavement Scientists and Engineers, Kansas City, USA.
of Asphalt Paving Technologists
``The Rational Design of Aggregate Gradings of Dense Asphalt Compositions'' by G.Lees presented at ``The Rational Design of Aggregate Gradings in Dense Asphalt Compositions''.
It is described in detail in a technical paper titled ``For Dense Asphaltic Compositions''. This article describes means of controlling porosity with respect to particle selection and physical properties. The tire treads and tires of this invention can be used in any size and application of vehicles such as motorcycles, cars, light and heavy vans, trucks, buses, coaches and airplanes. Embodiments of the invention will now be described with reference to the accompanying drawings. 1 is a sectional view of a tire according to the invention taken along a plane containing the axis of the tire; FIG. 2 is an enlarged plan view of a portion of the first tire tread as seen in the direction of the arrow in FIG. 1; Figures 3 and 4 are graphs showing the braking performance of two tires according to the invention and a comparative standard tire at two different speeds on a wet test surface; 4 is a graph showing the cornering performance of the three types of tires compared in FIG. 4 on a test surface at two different water depths. Referring to FIG. 1, this is a tire 1 according to the invention.
0 is shown, and the cross section is cut along a plane that includes the rotation axis of the tire 10. For example, tire 1
0 is a radial tire having a reinforcing layer 12 made of cords arranged substantially at 90 degrees in the circumferential direction of the tire, and both ends of the layer 12 are folded back around two bead cores 14. Also tire 1
0 includes a tread 16 and a tread reinforcement breaker 18 as is known in the tire art. In a typical tire, the tread 16 would be an otherwise solid, intricately grooved rubber layer integrally molded to the rest of the tire. However, in accordance with the present invention, the tread 16 is constructed as a porous layer of elastomeric material providing randomly communicating and randomly oriented passageways extending from the surface of the tread 16 over substantially the entire tread. It is formed. (The tire 10 may be other than a radial tire, such as a cross-layer tire or a belted bias tire). Toledo 16 that incorporates such Toretsudo
and some examples of how to form tires are shown below. The tire tread of the present invention can be incorporated into a tire by a retread installation method (ie, bonding to a used carcass) or as part of the tire manufacturing process. EXAMPLE 1 One method of making a tire according to the invention is to (i) make a tire strip according to the invention; (ii) make the tire strip based on uncured rubber with the binder used to make it; (iii) sanding the vulcanized tire casing;
Apply a standard thermoset tread solution to it; (iv) tread strips/undertreads;
(v) curing the assembly in a flat tread mold (i.e., an unpatterned mold). Example 2 Tread strips were manufactured by pouring a compact composition consisting of the following ingredients into wooden molds of the required dimensions. Granulated whole tire scrap consisting of bulked rubber particles with irregular shape and combined size less than 0.5 cc 500 vulcanized rubber selected to irregular shape and 10BS mesh (i.e. British Standard Sieve Number 10) Granulated whole tire scrap consisting of particles 1000 Hydroxyl-terminated liquid polybutadiene with a molecular weight of 2800 (R45M, manufactured by Arco) 360 Liquid methylene bisaniline diisocyanate containing higher functionality isocyanates (Suprasec DND, manufactured by ICI) 140 Carbon black pigment Dispersion 5 stannous octoate 0.2 After 24 hours, the mixture had hardened to a non-stick composite. a tire carcass is then prepared by scraping the tread off the car tire;
Carcass head R45M (10 parts), Suprasec DND
(4 parts) and stannous octoate (0.01 part). Then,
Apply tire tread strips to the carcass,
It was fastened to the carcass with tape and the ends of the strip were joined using the same adhesive composition. Expanding the tube within the carcass helped achieve intimate contact between the carcass and the tread strip. After 48 hours, the tape was removed, the tube was depressurized, and the finished tire was obtained. Example 3 (Use of Alternative Binder) An intimate mixture consisting of the following ingredients was poured into a mold of the required dimensions. Granulated vulcanized rubber consisting of generally uniformly sized particles having an average diameter of 0.5 cm and a hardness of 65 Shore A
100 pbw Adipren L-167 (isocyanate-functional polyurethane polymer, manufactured by Du Pont) 19 pbw Caytur21 (diamine curing agent, manufactured by Du Pont) 6 pbw Carbon black pigment dispersion 2 pbw Shape of tire tread by heating the mold to 120°C for 1 hour A product was obtained. Example 4 (Additional Binder) An intimate mixture of the following ingredients was poured into a mold of the required size. Granulated vulcanized rubber in Example 3 100pbw Mixture A 14.6pbw Diphenylmethane 4,4'-diisocyanate liquefied product (Isonate 143L, Upjohn) 10.2pbw Carbon black pigment dispersion 2pbw Stannous octoate 0.02pbw Mixture A is as follows: I was getting used to it. Alkyl oxide-terminated polypropylene glycol with a molecular weight of 2000 (propylan D2122, manufactured by Lankro)
100 pbw ethylene glycol 6.3 pbw trimethylolpropane 8.6 pbw After heating the mold to 80° C. for 1 hour, a product in the form of a tire tread was obtained. Example 5 (Method of manufacturing a tire having the tread of Example 3) A tread strip was manufactured by the method of Example 3 using the same component materials. A solution of triisocyanate in methylene chloride (Desmodur®, Bayer) was brushed onto one side of the tread and allowed to dry. A toluene solution of compounded natural rubber containing zinc oxide was then brushed onto the triisocyanate-treated surface and similarly dried.
The sticky side of the tread was then attached around the green tire carcass and the composite product was placed in a tire mold with a plain tread (ie, a non-patterned mold). A rubber tube is inserted into the carcass to adjust the unvulcanized rubber to the internal dimensions of the mold and to help bond the tread to the carcass.3.45
Inflated to bar pressure. The mold was then placed between the hot plates of a press and heated to 155° C. for 60 minutes, and then the completed tire was removed from the mold. Instead of bonding the particles together with a binder matrix, the particles may be fused together, or the materials of adjacent particles may be crosslinked at their points of contact, or the particles may be bonded together by adhesive or heat. Adhesion can be achieved by embedding in a curable plastic material. In order to obtain comparative performance results, two tires were manufactured as described in Example 2, but the tread of one tire was hereinafter referred to as "coarse tread".
1500 parts by weight of coarse particles of granulated rubber having a hardness of 60 to 70 Shore A and a particle size range of less than 0.5 cc to give a tire called ``tread''. The difference is that it was produced from fine particles consisting of 1000 parts by weight of granulated rubber having an average particle size selected for a cured 60-70 shore A and BS mesh to give a tire hereafter referred to as a "fine tread" tire. It was on. In either case, the initial trade was removed by buffing.
Combined with a carcass of 155SR13Dunlop SP4 tires. A standard 155SR13 Dunlop SP4 tire, still in its original tread, was tested to obtain results comparable to a normally treaded tire with the same carcass construction. All three tires were similarly inflated to the standard pressure of a 155SR13SP4 tire ("SP4" is a registered trademark), i.e. 1.8 Kg/ ^cm2 . Braking and cornering tests were conducted using an indoor drum tire testing machine. The apparatus was equipped with suitable force-measuring devices and was equipped with a device for delivering a stream of water at a controlled velocity onto the test surface of the drum to create a covered road condition with a predetermined depth of water. Graphs of brake force coefficient against slip percentage for coarse tread tires, fine tread tires and standard tread SP4 tires are shown in the third graph for equivalent vehicle speeds of 48 km/h and 80 km/h, respectively.
and shown in Figure 4. In both cases, the water velocity is
7.5/second, which is 48Km/hour and 3mm and
This simulates a road flooded with rain to an approximate depth of 1mm at 80km/hour. Figure 3 shows that both porous tread tires have a maximum braking force coefficient of about 3 times that of the standard tread SP4 at 48 km/h in very wet conditions, with the coarse tread tire performing somewhat better than the fine tread tire. It shows that there is. Figure 4 shows that at 80 km/h, both porous tread tires have almost the same good braking performance as at 48 km/h at the same water depth, but here the braking performance is about 8 times better than that of the standard tread tire. It shows that it is good. Figures 3 and 4 clearly show that the braking performance on wet roads of a tire according to the invention is substantially better than an otherwise identical tire having a conventional surface groove patterned tread. ing. The large number of randomly interconnected and randomly oriented passageways in the tread of the present invention allows water between the road surface and the tread portions in contact therewith to easily escape into the porous tread body; This prevents excessive accumulation of water that would otherwise reduce effective contact with the road and thus reduce braking performance. Water thus entrained into the tread body can escape laterally from the edges of the tread and also radially over the surface of the tread under centrifugal force as the tread leaves contact with the road during continuous rotation along the road. can. FIGS. 5 and 6 show graphs of changes in cornering force obtained by varying speeds for the same three tires whose braking performance is shown in FIGS. 3 and 4. In Figure 5, this water flow was 7.5/sec, but in Figure 6, the water flow was reduced to 1.0/sec. Figures 5 and 6 both show that at low speeds (below 16 km/h), all three tires had similar cornering ability, and that the porous tread tire showed only a slight decrease in cornering ability at significantly higher speeds (up to 100 km/h). However, conventional treaded tires suffered a significant reduction in cornering ability at these elevated speeds, and even more so on wetter surfaces (Figure 5). In general, the wet road cornering ability of fine-grained tread tires was only slightly better than that of coarse-grained treads. Further comparative testing of the three tires compared in Figures 3-6 was conducted to demonstrate the noise generating properties of each tread. 50Km/hour and 80 per 3 tires
The generated sound levels at speeds of Km/h are summarized in the table below.

Table: Thus, tires according to the invention are quieter in use than comparable conventional treaded tires. It has also been found that tires according to the invention have improved grip properties on icy roads than comparable conventional treaded tires. Thus, the present invention provides tire treads and such treads that have significantly superior wet grip capabilities and reduced noise production, yet eliminate the need for conventional intricately patterned and very expensive tread pattern forming molds. We provide tires that have

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a tire according to the invention taken along a plane containing the tire axis. 2 is an enlarged plan view of a portion of the tire tread of FIG. 1, taken in the direction of the arrow in FIG. 1; FIG. Figures 3 and 4 are graphs showing the braking performance of two tires according to the invention and a comparative standard tire at two different speeds on a wet test surface. In the graph, the horizontal axis shows the slip percentage (%), and the vertical axis shows the brake force coefficient. The line - indicates a coarse-grained treaded tire, -- indicates a fine-grained treaded tire, and 〓〓〓 indicates a standard SP4 tire. Figures 5 and 6 are graphs showing the cornering performance of the three tires compared in Figures 3 and 4 on test surfaces at two different water depths. In the graph, the horizontal axis shows speed (Km/hour) and the vertical axis shows cornering (Kg). 10...Tire, 12...Reinforcement layer, 14...Bead core, 16...Tread, 18...Breaker.

Claims (1)

Claims: 1. The elastomeric material is formed to provide randomly distributed and randomly oriented internal communicating passageways extending from the tread surface substantially throughout the tread 16. A tire consisting of a tread of elastomeric material. 2. A tire comprising the tread according to claim 1, characterized in that the porosity of the tread 16 is in the range of 10% to 60%. 3. A tire comprising a tread according to claim 1 or 2, characterized in that the average cross-sectional area of the passages is large compared to the cross-sectional area of the adjacent tread material bounding between the passages. 4. A tire comprising a tread according to claim 1 or 2, characterized in that the average cross-sectional area of the passages is small compared to the cross-sectional area of the adjacent tread material bounding between the passages. 5. Claims 1 to 4 in which the porosity is substantially uniformly distributed throughout the volume of the tread 16
A tire consisting of a tread according to any one of paragraphs. 6. A tire comprising a tread according to any one of claims 1 to 4, characterized in that the porosity varies in different regions of the tread (16) substantially according to a predetermined pore distribution pattern. 7. The pore distribution pattern is such that the porosity decreases with increasing distance radially inwardly from the tread surface in contact with the road when the tread 16 is in use. A tire comprising the tread according to item 6. 8. The pore distribution pattern is such that the porosity increases with increasing distance radially inwardly from the tread surface that contacts the road when the tread 16 is in use. Tire tread according to item 6. 9. The pore distribution pattern is such that the porosity decreases with increasing distance laterally inwardly from the lateral edge of the tread 16. A tire consisting of treads. 10. The pore distribution pattern is such that the porosity increases with increasing distance laterally inward from the lateral edge of the tread 16. A tire consisting of treads. 11. A tire comprising a tread according to any one of claims 1 to 10, characterized in that the tread (16) comprises a large number of discrete, irregularly shaped particles of elastomeric material. 12. A tire comprising a tread according to any one of claims 1 to 10, characterized in that the tread (16) comprises a large number of discrete, regularly shaped particles of elastomeric material. 13. A tire comprising a tread according to claim 11 or 12, characterized in that the particles have at least two different sizes. 14. A tire comprising a tread according to any one of claims 11 to 13, characterized in that the particles have a volume in the range from 6.5 x 10 ^-5 cc to 15 c.c. 15. A tire comprising a tread according to any one of claims 11 to 14, characterized in that the particles are bonded together to form agglomerates (16). 16. A tire comprising a tread according to claim 15, wherein the particles are bonded together by interparticle fusion. 17. A treaded tire according to claim 16, wherein the particles are comprised of uncured rubber and the interparticle fusion consists of crosslinking the material of adjacent particles at their points of mutual contact. 18. A treaded tire according to claim 15, characterized in that the particles are bound together into agglomerates (16) by a binder matrix. 19 The binder matrix consists of a binder material that solidifies upon curing and is bound together by forming a binder matrix with particles, the binder material being a reactive mixture that forms a polymer when cured. Claim 18, characterized in that
A tire consisting of the tread described in Section 1. 20 The reaction mixture consists of hydroxyl-terminated liquid polybutadiene and liquid methylene-bis-aniline-
A tire comprising a tread according to claim 19, characterized in that the tire comprises a diisocyanate. 21. The treaded tire of claim 19, wherein the reaction mixture comprises an isocyanate-functional polyurethane prepolymer and a diamine curing agent. 22 The reaction mixture consists of ethylene oxide-terminated polypropylene glycol, ethylene glycol, trimethylolpropane liquefied diphenylmethane 4.
20. A tire comprising a tread according to claim 19, characterized in that the tread comprises 4'-di-isocyanate. 23. A method for manufacturing a tire characterized by the step of bonding pulverized elastomeric material and forming it into the required shape of the tread 16. 24. A method according to claim 23, characterized in that the particles are joined by a step of interparticle fusion. 25. The method of claim 24, wherein the particles are comprised of uncured rubber and the interparticle fusion consists of crosslinking the material of adjacent particles at their points of mutual contact. 26. The particles are bonded to each other by forming a mixture of the particles and a binder, and then at least partially curing the formed mixture to form an agglomerate 16. The method according to scope item 23. 27. A method according to claim 26, characterized in that the forming method is carried out by extruding the mixture through a die whose orifice is formed in the desired cross-sectional shape of the tread. 28. Claim 27, wherein the further step of at least partially curing the formed mixture comprises the further step of at least partially curing the tread immediately after it exits the die. Method described. 29 The forming process consists of placing the mixture in a mold having the desired tread strip shape and dimensions, then allowing the mixture to at least partially harden in the mold, and finally removing the tread strip from the mold. 27. The method according to claim 26, characterized in that it is carried out by steps. 30. A method according to claim 29, characterized in that, because the mold is annular, the step consists in producing a tread in the shape of a seamless tread loop. 31. The method according to any of claims 23 to 30, comprising the steps of forming a tire tread 16, applying the tire tread 16 to a tire carcass, and bonding the tread 16 and carcass assembly. Method of manufacturing pneumatic tires. 32 forming the tire tread 16 and applying it to the carcass, bonding the assembly by placing the assembly in a mold and then curing the assembly in the mold by applying heat and pressure, and ensuring that the tire 10 is substantially completely Claim 3 comprising a further step of removing the tire 10 from the mold when cured.
The method described in Section 1. 33. The step of forming and applying the tire tread 16 to the tire carcass is carried out by placing the carcass in a mold and injecting a mixture of elastomer particles and binder material around the carcass in the mold;
The bonding step then comprises curing the carcass and tread material assembly in the mold by applying heat and pressure, and then a further step of removing the tire 10 from the mold when the tire is substantially fully cured. 32. A method according to claim 31, characterized in that the method is carried out. 34. Claim 31 characterized by a step consisting of preforming the tread 16 as a tread strip or tread band and then gluing the preformed tread to the tire carcass.
The method described in section. 35. The method of claim 34, further comprising the step of curing the tire carcass and the tire tread 16 adhered thereto in an unpatterned mold by applying heat and pressure.